Multiple language webshop

Im building a webshop and my customers wish is that it should be a multi-language one, so that everything including the product description would change language once the user clicks a language-flag on the page. Now i have read some disturbing topics about this on the forum, where there has been stated that this is not possible unless you pay 200€ / month, or by scripting, or by creating different shops for each language.

Now obviously if you want a shop in five different languages, you are not all that interested in adding a product five times over and over again :) also it is pretty hard to keep track of the stock controll. So i am now more interested in how javascript could help me, could it be possible to find a quick-tutorial, or an example on how this would work? has anyone tried PHP-include?

Thanks in advance